Large-scale production of proteins, such as antibodies, typically relies on secretion of the protein from a cultured production cell line. Secreted proteins produced by cultured cells can be readily recovered and purified from the surrounding cell culture media.
The cellular secretion rate of proteins is an important parameter affecting the production and purification of secreted proteins from a bioreactor or other system. In general, higher purified protein yields can be attained when the cellular secretion rate is relatively high. Conversely, if the cellular secretion rate is too low protein purification may not be feasible.
One approach to circumventing the problem of low secreting cells has been to isolate high secreting, subcloned cells from a population of low secreting cells. Typically, this requires several time and labor-intensive rounds of limiting serial dilution, screening and selection of high secreting cell lines. Alternatively, entirely new cell lines producing the protein of interest are generated in the hope that the new cell lines will be high secreting lines.
Each of the foregoing approaches to generating high secreting cell lines has limitations. For example, identifying high secreting cell lines by subcloning from a population of low secreting cells is limited by the relative rarity of high secreting cells in the population as well as the extensive amounts of time and labor required for the identification of any high secreting cells.
Further, the generation of new cell lines producing the antibody or protein of interest is limited by the possibility that the new cell lines will not be high secreting and the substantial amounts of effort required to re-generate antibody producing cells and identify high secreting cells. In some instances, only low secreting cell lines can be obtained due to protein misfolding inside the endoplasmic reticulum (ER) of the cell resulting in a decreased secretion rate.
Thus, a need exists for effective methods of changing the cellular secretion rate of a protein.